There has been known a vibration damping device, as a type of vibration damping device arranged between members to be connected to each other in a vibration damping manner, having a first mounting plate member and a second mounting plate member connected by a main rubber elastic body. Such a vibration damping device is used for an engine mount, a body mount or the like for motor vehicles, and in an FR (front-engine rear-drive) type vehicle, for example, it is generally arranged obliquely at respective positions diagonally below the engine of the power unit sandwiching the engine so as to support the power unit by the vehicle body in a vibration damping manner (see FIG. 1 of Patent Document 1).
In such a vibration damping device, a stopper mechanism is often provided to restrict not only the amount of elastic deformation of the main rubber elastic body but also relative displacement between members to be connected in a vibration damping manner. This stopper mechanism is constituted, for example, by means of installing a stopper plate to the first plate member in an overlapping manner to provide a stopper portion between a stopper plate and the second mounting plate member so that the first mounting plate member and the second mounting plate member get in contact with each other when they are relatively displaced.
However, an engine mount for motor vehicles, for example, requires the stopper function in various directions in order to restrict relative displacement of the power unit against the vehicle body, and it has been difficult to achieve the stopper function in various directions with a simple structure and a saved space. More specifically, in case of an engine mount for an FR type vehicle mentioned above, the stopper function is required not only against inputs in downward and left-right directions during regular driving but also against large inputs in the backward and diagonally upward direction at the time of vehicular collision.
Now, the inventor of the present invention designed, as shown in FIGS. 16 and 17 for example, a stopper mechanism that can perform the stopper function in multiple directions based on abutment of the stopper portions 3, 4 against the corresponding abutting portions 6, 7, respectively, by means of forming the stopper portions 3, 4 on a pair of opposing sides of the stopper plate 2 overlapped with the first mounting plate member 1, while providing the pair of abutting portions 6, 7 at corresponding positions on the second mounting plate member 5. This stopper mechanism was designed to perform the stopper function by cutting an opening window 8 on the stopper portion 3 and outwardly extending the plate-shaped engaging piece 9 that protrudes from the abutting portion 6 through the opening window 8, and then abutting the stopper portion 3 against the engaging piece 9 of the abutting portion 6 between the first and second mounting plate members 1, 5 also in the direction of separating from each other.
However, according to further studies by the inventor of the present invention, it was found that there is a risk of not being able to perform the intended stopper function in a stable manner, once the input load in the backward and diagonally upward direction becomes excessive as a consequence of weight increase of the power unit resulting in an increase in the amount of deformation of the stopper portion 3 provided with the plate-shaped engaging piece 9 and the opening window 8.